1. Field of the Invention
The present invention relates to a piercing apparatus and piercing method which drive a columnar shaped punch in an axial direction to pierce a hole in a workpiece.
2. Description of the Related Art
In the past, in a piercing apparatus which pierces a hole by stamping using a punch, there was the issue that the larger the ratio between a length L and diameter D of the hole (hereinafter, referred to as the “L/D”), the greater the possibility of the punch buckling became. Therefore, a piercing apparatus which can pierce a hole, without using a punch, by electro-discharge machining or laser cutting has been considered.
In this regard, when using electro-discharge machining to pierce a hole, there is the issue that the processing time becomes longer than with stamping and the productivity therefore falls. Further, when using laser cutting to pierce a hole, while the drop in productivity can be avoided, there is the issue that the dimensional precision of the hole, the surface properties, and other aspects of work quality become inferior compared with stamping or electro-discharge machining. Therefore, for the purpose of achieving both good productivity and work quality, for example, the piercing apparatus described in Japanese Patent Publication (A) No. 2009-050901 has been proposed.
The piercing apparatus of Japanese Patent Publication (A) No. 2009-050901 is provided with a laser head, punch, and die and pierces a hole by jointly using laser cutting and stamping. That is, according to the piercing apparatus of Japanese Patent Publication (A) No. 2009-050901, laser cutting is used to pierce a rough hole in a workpiece, then a punch larger in diameter than the rough hole is used to stamp the workpiece so as to cut away the peripheral edges of the rough hole. Due to this, the piercing apparatus of Japanese Patent Publication (A) No. 2009-050901 tries to achieve both good productivity and work quality while reducing the possibility of the punch buckling.
However, according to the piercing apparatus of Japanese Patent Publication (A) No. 2009-050901, axial alignment of the rough hole formed by the laser and the stamping by the punch was complicated and created a new issue.